1. Field of the Invention
This invention relates to a fuel cell device and, more particularly, to a fuel cell device comprising a polymer electrolyte fuel cell in which an anode and a cathode are arranged at both sides of a polymer electrolyte membrane.
2. Description of the Prior Art
In general, a polymer electrolyte fuel cell in which an anode and a cathode are arranged at both sides of a proton-conductive polymer electrolyte membrane is known as a fuel cell. In the polymer electrolyte fuel cell, fuel gas including hydrogen is supplied to the anode and oxidation gas such as air is supplied to the cathode, whereby the electrochemical reaction is generated to shift proton in the polymer electrolyte membrane, to thereby produce electromotive force. This polymer electrolyte fuel cell is known as an energy-efficient fuel cell that can convert chemical energy of the fuel gas to electrical energy directly.
In this polymer electrolyte fuel cell, temperature of the polymer electrolyte membrane must be controlled to a predetermined temperature in order for the fuel cell to generate electric power in most safety and with high efficiency. Because of this, the typical polymer electrolyte fuel cell is so designed that a flow path of cooling water is formed in an interior of the fuel cell so that the cooling water can be circulated through the flow path to reduce heat generated when electric power is generated.
Cited as this typical fuel cell device are those disclosed, for example, in Japanese Laid-open Patent Publications No. Hei 6(1994)-188013 and No. Hei 10(1998)-340734 and shown in FIG. 7. In FIG. 7, there is shown a fuel cell device in which a fuel cell 1 and a radiator 2 are connected to each other through a closed line by cooling pipes 3. Provided between the cooling pipe 3 located upstream of the fuel cell 1 and the cooling pipe 3 located downstream of the radiator 2 is a pump 4 for feeding cooling water therebetween. In this fuel cell device, with the drive of the pump 4, the cooling water is sequentially circulated through between the fuel cell 1 and the radiator 2 to feed the cooling water cooled by the radiator 2 to the fuel cell 1, so as to cool the fuel cell 1. The cooling water warmed after having cooled the fuel cell 1 is flown back to the radiator 2, so as to be cooled down again by the radiator 2. A fan 5 is provided at a location facing the radiator 2 to cool the radiator 2 by it, so as to promote heat release of the radiator 2. A feed water tank 6 is connected to the radiator 2.
The fuel cell device shown in FIG. 7 is provided with the water feed pump 4 and the fan 5 for cooling the radiator 2, so a part of the electric power generated is consumed as the power for driving the pump 4 and fan 5. Thus, the fuel cell device of FIG. 7 suffers from the disadvantage of inevitable loss of a part of the electric power generated.
In addition, the provision of the pump 4 and the fan 5 provides a complicated structure of the device and an increased cost and also requires a space therefor, thus involving the disadvantage of upsizing of the device.
It is the object of the present invention to provide a fuel cell device that can well circulate cooling medium with simplified and compact construction, without any need of a driving device for feeding the cooling medium, to reduce electric power loss.
The present invention is directed to a novel fuel cell device comprising a fuel cell in which an anode and a cathode are arranged at both sides of a polymer electrolyte membrane; an inflow-side cooling pipe, connected to the fuel cell, for letting a cooling medium flow in the fuel cell; an outflow-side cooling pipe, connected to the fuel cell, for letting the cooling medium flow out from the fuel cell; and a heat release means to cool down the cooling medium, the inflow-side cooling pipe and the outflow-side cooling pipe being connected to the heat release means, wherein the heat release means is disposed at a position higher than the fuel cell and open to outside air.
With this configuration, heat generation involved in the electric power generation of the fuel cell raises the temperature of the cooling medium flowing out from the fuel cell and decreases the density. This causes the cooling medium to rise through the outflow-side cooling pipe and flow into the heat release means. Then, the heat release means heat-exchanges the cooling medium flown therein and the outside air, to cool down the cooling medium. The cooling medium as cooled down and thus increased in density lowers through the inflow-side cooling pipe and flows into the fuel cell again. With this flow, the cooling medium circulates through between the heat release means and the fuel cell and, as a result of this, the fuel cell is well cooled down by the cooling medium. Hence, there is no need to provide any additional driving device, such as a pump, for feeding cooling medium, so that a part of the electric power generated can be prevented from being consumed for driving such a driving device. Hence, the electric power loss can be reduced to achieve an effective supply of the electric power. Besides, complication of the structure of device and upsizing of the device that will be caused by the provision of some additional driving device can be avoided and accordingly reduction of cost and size resulting from the simplified structure of the device can be achieved.
In this configuration, it is preferable that the inflow-side cooling pipe is connected to the fuel cell at a position lower than a position at which the outflow-side cooling pipe is connected to the fuel cell.
With the structure in which the inflow-side cooling pipe is connected to the fuel cell at a position lower than a position at which the outflow-side cooling pipe is connected to the fuel cell, the cooling medium of increased density flown out of the heat release means can smoothly be fallen and fed into the fuel cell, while also the cooling medium of decreased density flown out of the fuel cell can smoothly be raised and fed into the heat release means. This can ensure further smooth circulation of the cooling medium through between the heat release means and the fuel cell to yield further improved cooling efficiency.
The fuel cell device of the present invention is preferably loaded in an automobile. In this embodiment in which the fuel cell device is loaded in the automobile, for example when the automobile increases in speed, on the one hand, the fuel cell generates more electric power, so that heat generation involved in the power generation raises the temperature of the cooling medium flown out of the fuel cell; on the other hand, the heat release means gets higher winds in itself to the extent corresponding to the increased speed, so that the cooling medium flowing into the heat release means is cooled down with further efficiency to the extent corresponding to the raised temperature. When the automobile is in idle engine operation, on the one hand, the heat release means gets no winds in itself, so that the cooling medium flown in the heat release means is not cooled down with efficiency; on the other hand, little heat is generated from the power generation of the fuel cell, so that the cooling medium flowing out of the fuel cell does not rise to a high temperature and thus no inconvenience is caused. Thus, cooling efficiencies of the heat release means can be varied in accordance with temperature of the cooling medium that varies in accordance with the electric power generated by the fuel cell, without any particular device therefor. Hence, the efficient cooling of the fuel cell can be achieved with simple constitution.
In this embodiment, it is preferable that an air spoiler having a wing portion extending in a widthwise direction of the automobile and legs supporting the wing portion is mounted on the automobile, and the heat release means is disposed in a place under the wing portion.
With the configuration in which the air spoiler is mounted on the automobile and also the heat release means is disposed in a place under the wing portion of the air spoiler, the air spoiler produces downforce so that increased stability of the automobile can be produced when travelling at high speeds. In addition, the air spoiler acts to collect the winds and feed them to the heat release means, so that further improved cooling efficiency of the heat release means can be produced. As a result of this, the heat release means of compact design can be provided and also improved design can be provided by integral combination of this heat release means with the air spoiler.
Further, when the heat release means is disposed under the air spoiler, it is preferable that the heat release means is disposed under the wing portion on a rear side thereof with respect to a longitudinal direction of the automobile.
With the configuration, the heat release means disposed under the wing portion on the rear side thereof with respect to a longitudinal direction of the automobile can let more winds in, as compared with the heat release means disposed under the wing portion on a front side thereof, to produce a further improved cooling efficiency.